The present invention relates generally to phase shifting devices and more particularly to millimeter-wave phase shifting devices utilized at high millimeter-wave frequencies.
Phase shifting devices are commonly used at millimeter-wave frequencies, but have generally been limited except in experimental devices to use with frequencies below 35 gigahertz. These devices have been designed to transmit the dominant mode of the millimeter-wave energy. However, it is practically impossible to fabricate these devices for use in the high frequency range of 60 gigahertz and above, due to the small size and extremely high tolerances required in the dominant-mode device.
For example, the cross-section of a typical ferrite phase shifter is about 0.25 inches at 10 GHz. At 100 GHz, the cross-section is 0.025 inches, and the absolute tolerances ten times as stringent. Also, the high field concentration in the region of transition from standard waveguide to ferrite severely limits the power handling capability of such a phase shifter, even if it could be built. To date, due to these high tolerances and power limitations, no practical phase shifters of the conventional designs have been made for use at high millimeter-wave frequencies.
A discussion of several conventional phase shifters of related design may be found in publications entitled "A Dual Mode Latching, Reciprocal Ferrite Phase Shifter", by Charles R. Boyd, Jr., "An X-Band Reciprocal Latching Faraday Rotator Phase Shifter", by R. G. Roberts, and "An S-Band, Dual Mode Reciprocal Ferrite Phaser For Use At High Power Levels", by C. R. Boyd, Jr. et al, all published in IEEE G-MTT International Microwave Symposium Digest, 1970.
Accordingly, it would be an improvement to the phase shifting art to provide for a phase shifter which could be utilized at high millimeter-wave frequencies while allowing ease of manufacture. In addition, it would be an improvement to provide for a high frequency millimeter-wave phase shifter which could be used at high power levels.